Some aging mice display symptoms quite similar to those found in the aging human with presbycusis: perceptive hearing loss which is most extreme at high frequencies, with associated damage to the organ of Corti. We will examine several inbred strains of mice, utilizing a nonintrusive method of repeatedly obtaining auditory nerve and brainstem evoked responses (BSER's). We will trace the development of these threshold and suprathreshold electrophysiological events and correlate them with behavioral thresholds, suprathreshold behavior, and histological examination of the inner ear and brainstem. Interaction of genotype with environmental factors (noise, ototoxic drugs) will be examined. Since these electrophysiological techniques can be non-traumatically applied to humans, the mose studies may be directly compared to the human condition, and screening procedures may be developed for agents and techniques which can prevent or retard age related hearing loss in man.